Nonchalking coating composition



No Drawing.

Patented June 20, 1933 UNITED STATES PATENT OFFICE JOHN WATSON GILBERT,OF PARLIN, NEW JERSEY, ASSIGNOR TO E. I. DU PONT DE NEMOURS & COMPANY,OF -WILMINGTON, DELAWARE, A CORPORATION OF DELA- WARE This inventionrelates to paints or lacquers made from cellulose derivatives and moreparticularly to non-chalking paints containing antimony oxide. l

Pyroxylin enamels in general, and particularly those containingconsiderable quantiti-esof the commonly used white pigments, such aszincoxide, lithopone, etc., have an inherent tendency to chalk upon exposureto the weather. This chalking is essentially a surface effect due to avery gradual, superficial disintegration of the protective film whichreleases the pigment particles. As the period of exposure progressesthis chalking gradually increases until finally the film when exposed tothe weather is almost completely destroyed due to washing away anderosion. Obviously, this effect is undesirable from several viewpoints.For example, chalk gives a dull, lifeless appearance to a finish such asthat applied to an automobile and necessitates frequent washing andpolishing to keep the finish in a satisfactory condition. Furthermore,the wearing or washing away of the chalk gradually decreases filmthickness, eventually resulting not only in complete loss 1 ofprotection but also in poorappearance.

I have found that all of the commonly used white pigments will chalk ina pyroxylin vehicle when exposed to the weather. Zinc oxide," which isprobablythe most widely used white pigment for lacquer, chalks considerably {when used alone or in combination with other pigments.Titanox and pure titanium oxide, which are pigments resembling eachother, show excessive chalking onexposure 1n pyroxylin vehicles. Thesepigments likewise chalk badly when exposed in paint or dryingoilvehicles. I Lithopone, another white pigment, is not durable on outdoorexposure in pyroxylin vehicles and is therefore not generally used inoutside lacquers.

This invention has as an object, to provide a new pigmented cellulosicpaint or lacquer. Another object is to provide a paint capable ofproducing a coat or. film which is not subject to chalking when exposedto the weather or other erosive conditions and which:

will effectively retain its original luster. Other objects will appearhereinafter.

NONOHALKING COATING COMPOSITION App1ication\ filed January 3, 1929.Serial No. 330,147.

I Ewample 1 Percent Low viscosity nitrocellulose 1O Damar resin 3 Estergum Castor oil 3 Dibutyl phthalate s 3 Antimony oxide 15 Solvents anddiluents 66 Ewample 2 P crcen Low viscosity nitrocellulose Damar resin 5Ester gum Castor oil 3 Dibutyl phthalate Antimony oxide Q. 15 Solventsand diluents (it I Example 3 Per cent Low viscosity nitrocellulose 1ODamar resin--. Ester gum Castor oil 3 Dibutyl phthalate 3 Antimony oxide25 Solvents and diluents l 54 I 100 Emampic 4 Percent Low viscositynitrocellulose 10 Damar resin 2.5 Ester gum 2.5 Castor'oil 3 Dibutylphthalate 3 Antimony oxide 15 Solventsand diluents. 64

The above examples do not include zinc oxide, titanium oxide orlithopone and the compositions coming Within the scope of this inventionare substantially free of the above commonly used pigments. It has beenfound that a film having appreciably improved resistance to chalkingcannot be obtained according to the present invention where Zinc oxide.titanium oxide or lithopone are present in appreciable amounts.

It is to be understood that I may make many modifications in theformulation of my improved coating composition within the scope of myinvention.

For example, the incorporation of the antimony oxide into the vehiclemay be accomplished by any of the accepted methods now in use in thepaint, lacquer or allied industries, such as grinding in roller mills,buhr stone mills, pebble or ball mills, or in any other convenientmanner.

Although I prefer to use a low viscosity pyroxylin, I may use pyroxylinof various types and viscosity characteristics. Furthermore, I may useother cellulose derivatives than pyroxylin, such as cellulose acetate,etc. It is obvious that the amount of cellulose derivative employed inmaking up any par ticular composition will depend on the type andviscosity of the product desired.

I may use either natural resins, such as rosin, shellac, elemi, damargmn, etc., or synthetic resins, such as 'cumaronc, amberol, ester gum,or their equivalents.

Furthermore, I may use various types of oils. These may be either dryingoils or non-drying oils, or both. Typical of the drying oils are linseedand chinawood oils, while among the non-drying oils may be mentionedcastor oil, stearic acid, etc.

I may employ various plasticizing agents, such as dibutyl phthalate,trioresyl phosphate, triphenyl phosphate, etc., either alone or invarying combinations.

Again, the cellulose derivative may be dissolved in a variety ofsolvents or solvent combinations, either with or without the addition ofdiluents. It is, of course, obvious that the solvents and diluentsselected will depend upon the type of cellulose derivative employed andalso upon the desired characteristics of the coating composition.

It is also to be understood that the antimony oxide pigment may be usedalone or in combination with various other pigments or coloring matterwithin the scope of my invention.

- My improved non-chalking coating composition may be used as aprotective or decorative coating for many objects which are intended forindoor use, such as refrigerators, furniture. toys, novelties, brushhandles. etc. It finds particular application as a protective coatingfor surfaces exposed to severe weather conditions, such as the finish ofautomobiles, railroad cars, and other vehicles.

Heretofore, coating compositions consisting of cellulose derivatives,resins, oils, plasticizers, solvents and diluents would chalk and wearaway badly 011 exposure when the ordinary pigments were employed intheir formulation. For example, a film consisting ofI'llt-l'OCQlllllOSG, resin, oil, plasticizer, and zinc oxide will becomechalked and completely worn away within a relatively short time, while acoating composition made according to my invention and containingantimony oxide as a pigment exhibits practically no chalk nor indicationof erosion or wearing awav after continued exposure for a period as longas three years.

This chalking efl'e'ct characteristic of the ordinary types of filmproduced from present paints and lacquers soon gives rise to a loss ofluster and consequent spoiling of appearance, but by the. use of thecoating material of my invention, a film may be produced which willretain its luster indefinitely. Ordinary films require frequent cleaningand polishing to retain a satisfactory appearance, but with a filmproduced from the composition above described, this labor is reduced toa minimum. It will thus be apparent that I have produced a veryeffective, resistant, non-chalking coating composition.

' As many apparently widely different embodiments of this invention maybe made without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. A- coating composition adapted to give films resistant to chalkingconsisting of low viscosity cellulose nitrate, damar resin, ester gum,astor oil, dibutyl phthalate, antimony oxide. solvents and diluents.

A coating composition adapted to give tilms resistant to chalkingcon'iprising a cellulose derivative vehicle and antimony oxide, saidcellulose derivative vehicle being of the type which is adapted to give.chalking films with zinc oxide, titanium oxide or lithopone and saidcoating composition being substantially free of the pigments, zincoxide, titanium oxide and lithopone.

3. A coating composition adapted to give tihns resistant to chalkingcomprising a cellulose nitrate vehicle and antimony oxide, saidcellulose nitrate vehicle being of the type which is adapted to givechalking films with zinc oxide, titanium oxide or lithopone and saidcoating composition being substantially free of the pigments, zincoxide, titanium oxide and lithopone.

In testimony whereof. I aflix my signature.

JOHN WV. GILBERT.

